An introduction to pigments
The first known painters 17,000 years ago took the things around them which had a strong colour like burnt wood, red earths and crushed them with water to create paint. Now there is a bewildering amount of pigments available, however they do fall into distinct categories and it is helpful to know a little about this.
A pigment is a coloured substance which imparts its colour to another material when it is mixed with it or applied over it's surface in a thin layer, if the pigment is dispersed within a medium it does not dissolve, if it dissolved it would be classed as a dye.
Generally pigments are placed in two groups inorganic and organic, inorganic basically means it has been derived from a mineral, so that includes all the earths like raw sienna and burnt umber but also the artificially prepared mineral colours like the cadmiums and cobalts.
Organic generally means derived from an animal or plant, historically these were a massively important part of pigments and dyes with products like indigo and cochineal literally propping the economies of several countries. A lot of these have been replaced using chemistry to provide more stable and light fast colours, it is also a lot more humane way of producing colour, cochineal involved crushing billions upon billions of small insects and indigo relied massively on slave labour.
However possibly the hands down winner for animal cruelty in the pursuit of colour was Indian Yellow, which was made by force feeding cows mango leaves and then heating their urine to concentrate the colour, given cows are sacred in India it is yet another example of the British Empire's dubious practices.
Please no more mango leaves!
There are a few terms which crop up quite a bit in describing pigments in oil paint I will explain a few of them now.
Earths are the first I would like to mention, these are my favourite range of colours and the oldest man has used there is something very satisfying painting with an earth colour knowing it is so simple just oil and earth, the 'earth' is basically crushed rock or a washed clay. They have all those inherent natural imperfections which refract light in so many ways and you are following in the footsteps of the greats, all the Italian renaissance painters, the Dutch masters all relied heavily on the earths.
The most familiar earths would be the ochres, siennas and the umbers, heat can be applied to all the earths in order to change the colour as you would imagine it tends to darken the existing colour and the more it is heated the more permanent it becomes, this gives us colours like burnt umber and burnt sienna.
As it is an entirely natural product the grades and varieties vary depending on the geographic location, the most obvious is sienna with the finest grades coming from Siena in Italy. The best ochres tend to come from France and the best umbers from perhaps surprisingly from Cyprus. In my opinion the greatest manufacturer of earth paint is Rublev, their range and quality is unsurpassed and you can learn more about the earths by looking at our range of their paints, they go from cool greens to very warm reds.
It is the presence of Iron Oxide in most of these rocks and clays which gives the colours and you can also buy artificial Iron Oxide paints where you will get similar colours but with more consistency and less variation these are referred to as mars colours, for example mars yellow and mars violet.
I prefer the natural ones as I believe you will get more depth in the paint as the light is refracted much more randomly with the natural imperfections, however it depends on what you are trying to achieve and a lot can be said be the uniformity and handling of the mars colours.
Below is a picture of a volcano where the rock for Rublev's Ercolano Red is mined you can make out the orange red streaks down the side.
The next term you may come across is 'lake'. A lake in relation to paint refers to a quite complicated process of dying an inert substance in order for it to behave like a normal pigment. If you imagine a fine dull white powder and adding to that a powerful dye which will dissolve and stain the powder permanently that is essentially a lake pigment, some of the most luminescent colours a painter can access are lakes.
They can be stunningly beautiful, Alizarin Crimson springs to mind this is an intense pinkish red and completely transparent, you can almost see it vibrating.
Briefly going back to organic and inorganic pigments, inorganic Alizarin Crimson replaced the organic madder pigment, derived from the madder plant, which was the source of a huge business, the madder plant supplied half the world's red in 1800, why was it replaced? Because the Alizarin was cheaper to produce and more lightfast.
The inert base for a lake tends to be Alumina Hydrate which when mixed with oil becomes practically invisible, although the base can also be derived from clays but paints made this way tend to have a loss in tone. An exception to this is, are green lakes which are usually 'fixed' onto green earths.
There was a renaissance in painting, few people know there was also a renaissance in pigments...